Area Forecast Discussion
Issued by NWS Honolulu, HI
FXHW60 PHFO 280719
Area Forecast Discussion
National Weather Service Honolulu HI
919 PM HST FRI MAY 27 2016
A weak front northwest of the state will keep winds light through
the weekend. This front will push slowly southward through Kauai
and Oahu Sunday night and Memorial Day, before stalling out and
dissipating over the central and eastern islands by mid week. High
pressure will build north of the state in the wake of the front,
allowing the trade winds to return for much of next week.
Currently at the surface, a 1029 mb high is centered around 1550
miles northeast of Hilo. Meanwhile, a nearly stationary front
resides around 350 miles northwest of Kauai. Infrared satellite
imagery shows partly to mostly cloudy skies in place across the
state, with radar imagery showing scattered showers slowly
diminishing in most areas. Main short term concern for tonight
revolves around rain chances.
High pressure northeast of the state will remain nearly
stationary, while the front northwest of Kauai moves very little
as well. This will keep a light wind regime in place across the
western islands, with light trades continuing across the eastern
half of the state. At the same time, some weak shortwave energy
will be moving through overhead, and the airmass will remain
fairly moist with precipitable water (PW) values remain between
1.3 and 1.6 inches through the night. As a result, showers will
be possible in most areas through the night, with highest rain
chances across windward areas due to the terrain enhancement
resulting from light east-southeasterly flow.
Saturday through Sunday...
The front northwest of the islands will push slowly southeastward
through the period, and will be approaching the coast of Kauai by
late Sunday afternoon. As a result, the light wind regime will
remain in place across the state, with daytime sea breezes and
overnight land breezes expected in most areas. PW values will
remain around 1.5 inches through the period, so expect mainly
afternoon and evening showers over the interior of the islands
Sunday night through next Friday...
The 00z GFS and 00z ECMWF offer slightly different solutions with
respect to the front entering the island chain early next week.
Despite the minor differences in timing details, they both
suggest that a weakening front will move southward through Kauai
and Oahu early next week. The front is then expected to stall out
and slowly dissipate over the central and eastern islands through
mid week as high pressure builds north of the state. We will
utilize a blend of the 00z solutions through the period which
suggests some enhanced showers moving southward through the island
chain in association with the weakening front on Memorial day and
through the first half of the week. Showers should also begin to
focus more across windward and mauka locales as the week
progresses due to returning trades resulting from high pressure
building north of the state. A more typical trade wind pattern
will return for the second half of next week as PW values drop
closer to seasonal levels and light to moderate trades continue.
As the prevailing wind flow remains east-southeast, much of the
smaller islands will remain in the light wind regime with land
breezes at night and sea breezes during the day. Afternoon
convection over the islands will be decreasing, though low clouds
may linger through this evening before clearing out overnight.
Expect mainly VFR conditions to prevail for all areas, though
lingering low clouds may bring MVFR ceiling briefly through the rest
of the evening.
Therefore, the AIRMET for mtn obsc is still expected to be cancelled
in the coming hours, though may return again by Saturday afternoon
as another round of convection develops.
Winds and combined seas will remain below small craft advisory
criteria through the forecast period.
The current southwest swell will gradually diminish through the
holiday weekend. A small northwest swell arriving Sunday will
peak Monday well below the advisory threshold. See the the
Collaborative Near-shore Swell and Wind Forecast (SRDHFO) for
details on these swells. Otherwise rather small surf is expected.